1. Field of the Invention
The present invention relates to furnaces which may be retrofitted with a flue damper. More specifically, the invention relates to the wiring circuits and connections for installing a retrofit flue damper within a furnace.
2. Description of the Prior Art
The energy shortages that have become apparent in the last ten years have spurred society towards reducing the energy consumption of existing furnaces as well as designing more efficient future heating devices. In response to this demand for reducing energy consumption renewed interest has focused on regulating energy losses which occur when flue gases carry residual heat through an exhaust flue away from an enclosure to be heated and when cold outdoor air enters the enclosure through the open exhaust flue. By the installation of a flue damper the flue gas passage can be open when the furnace is producing heat to allow for the escape of flue gases and closed when the furnace is not producing heat, thereby eliminating heat losses through the exhaust flue.
Public utilities, the American Gas Association and Underwriters Laboratories have generally prevented the use of flue dampers in furnaces for various safety reasons. If the flue damper does not open during fuel combustion incomplete burning occurs allowing flue gases to build up and creating the potential for the enclosure to be heated to be filled with quantities of carbon monoxide. Furthermore, if the flue damper is not open during combustion, unburned fuel, such as natural gas may be leaked into the enclosure creating the possibility of explosion and fire.
U.S. Pat. Nos. (3,664,414) issued to Raleigh; (3,587,558) Raleigh; (3,223,137) Grahl and (3,544,003) Bissel all concern furnace circuits but not the adaptation of a retrofit flue damper thereto. Various methods and apparatus are known and disclosed in the following United States Patents for removing a portion of a conductor from a printed circuit board: U.S. Pat. Nos. (3,728,471) Blinkhorn; (3,601,522) Lynch; (3,532,802) Spall; and (3,898,370) Davy. None of these references discloses the use of a removable jumper portion of the printed circuit board for preventing the attachment of an electrical connector prior to the removal of the jumper portion.
Other United States Patents relating to connectors for printed circuit boards include U.S. Pat. Nos. (3,140,908) McCutchon; (3,818,280) Smith et al; (3,780,431) Feeney; (3,533,045) Henschen; and (3,425,021) Fow et al. Again, none of these patent references disclose the removal of a portion of the printed circuit board before the connector can be attached.